1. Field of the Invention
The present invention relates to a device for measuring the substrate temperature of an integrated circuit chip.
2. Discussion of the Related Art
In many electronic systems, it is desired to be able to measure, in operation, the internal temperature of an integrated circuit chip. It is especially desired to detect possible abnormal rises in the chip temperature.
Temperature measurement devices have been based on the observation of the variations of the value of a resistor formed in the substrate of a chip. Indeed, since silicon has piezoresistive properties, the value of a resistor formed in a silicon substrate depends on the mechanical stress undergone by the substrate. Since temperature variations cause stress variations in the substrate, the resistance value is linked to the substrate temperature.
A disadvantage of this type of temperature measurement devices is their inaccuracy, especially due to the inaccuracies of resistor manufacturing methods. Indeed, at equal temperature, value differences can be observed between resistors formed in different chips of a same semiconductor wafer, and even more between resistors formed in separate chips of different semiconductor wafers.